There is known an apparatus for deburring workpieces by gas detonation (cf., U.S. Pat. No. 3,666,252, Int. Cl. C 21 D 1/82) comprising a bed the upper part of which accommodates a casing with a cavity open at one, particularly lower end. Mounted on the bed is an indexing table on which there are disposed equidistantly about the periphery replaceable bottoms arranged alternately opposite to the open end of the casing.
Secured under the casing on the bed is a drive for imparting reciprocating movement to each successive bottom in a direction to the casing and therefrom. The drive has the form of a toggle driven by a hydraulic power cylinder and kinematically linked with a pusher extending through hole in the indexing table provided under each replaceable bottom. The pusher is intended to lift the bottom from the indexing table, move the bottom and force it to the open end of the casing.
As the casing is connected to one of the bottoms, a gas detonation chamber is formed intended to accommodate therein workpieces having burrs to be removed especially in hard-to-reach locations by gas detonation, that is by explosion of a gas mixture. The force developed by the hydraulic power cylinder is sufficient to hold the gas detonation chamber sealed at the point of gas detonation.
Each bottom has at its top a sealing element serving to hermetize the interior of the gas detonation chamber at the point where the bottom is connected to the casing.
For feeding a combustible gas and oxygen to the gas detonation chamber to form an explosive mixture there is provided a gas feeding system, whereas a spark plug is envisaged for igniting the gas mixture.
In this prior art apparatus the bed and toggle operate under heavy static loads as the bottom is connected to the casing, that is when the gas detonation chamber is closed and sealed, and as high dynamic loads are developed following a sudden increase in pressure in the chamber during gas detonation, viz., during explosion of the mixture.
A specific feature of the process of explosion taking place in the gas detonation chamber is such that in the case of depressurization of this chamber at the point of explosion (the pressure accompanying the explosion being intended to open the gas detonation chamber, viz., to force the bottom away from the casing) hot products of explosion can escape, whereby the elements of the gas detonation chamber tend to fuse resulting in burning and failure. Therefore, highly reliable sealing of the gas detonation chamber during gas detonation in such apparatus is essential.
Further, in this known apparatus the force connecting the casing to the bottom is controlled by varying resilient displacements of the bed as the gas detonation chamber is closed. Since the bed is subjected to substantial loads, it has to posess a sufficiently high rigidity and therefore be quite bulky, whereby during closing of the gas detonation chamber the bed is subject to small resilient displacements which are virtually impossible to measure.
When closing the gas detonation chamber, the levers of the toggle are set along a straight line to prevent gas detonation from acting on the hydraulic power cylinder. However, during operation the friction parts of the toggle tend to wear to result in play, which is practically impossible to eliminate, because the levers are in one line. Therefore, the magnitude of minor resilient displacement of the bed must be constantly controlled, and when necessary, thorough adjustment of the closing force must be done, which necessitates the services of highly qualified adjusters.
For removing burrs from workpieces of larger size, it is necessary to increase the dimensions of the gas detonation chamber. This in turn leads to higher loads exerted on the toggle and, accordingly, on the bed to necessitate their higher rigidity, greater weight, and higher powder of the hydraulic power drive ensuring closing or sealing of the gas detonation chamber.